Method and device for flow analysis

ABSTRACT

A method and a device suitable for carrying out the method are proposed for analyzing and quantifying flows, in particular for the three-dimensional determination of flow velocity components or the three-dimensional visualization of flows in fluids or gases. For this purpose, electromagnetic waves, especially light, are detected, which at least partially emanate from or are scattered by particles that are contained in the detection space and that characterize the flow to be analyzed, the waves being detected using at least one detection device, in the form of two-dimensional images that are recorded in a frequency-selective or frequency-band-selective manner, from which the flow is determined. The illuminating device for this purpose generates at least two, at least approximately parallel light sheets, arranged in spatial succession, generated in temporal succession, having electromagnetic waves of different frequencies or different frequency spectrums, which scan the detection space at least in areas.

FIELD OF THE INVENTION

The present invention relates to a method and a device for the analysisand quantification of flows, in particular for the three-dimensionaldetermination of flow velocity components or of the three-dimensionalvisualization of flows in fluids or gases.

BACKGROUND INFORMATION

Measuring flow velocities and visualizing flows have broad applications,especially in aerodynamics and in fluid dynamics, in the analysis andoptimization of the most varied flow phenomena, as well as in the areaof industrial process engineering and production technology. In thiscontext, mechanical, electromechanical, as well as optical flowmeasuring methods are used. The existing optical flow measuring methods,in this regard, can be roughly subdivided into point, surface, andspatial measuring methods.

In this way, the surface measurement of intermittent flow processes orof spatial turbulence structures has been possible heretofore usingso-called total-field methods. These methods detect in liquid or gasflows the scattered light of particles suspended therein in lightsections or a light-section sheets.

In addition, in the case of surface measuring methods, so-called“Particle Image Velocimetry (PIV)” and the “Particle Tracking Method”are widely used. In this context, the shift of suspended particle groupsor of individual particles that are suspended in a medium that is to beanalyzed is determined with respect to the flow conditions usingcorrelation, or tracking, algorithms.

In addition, in surface measuring methods, it is known to use twodifferent, colored light sections, at the same time, for determining thenormal velocity components of the suspended particles perpendicular tothe light-section sheets. In this regard, reference should be made, byway of example, to I. Kimura and Y. Kohno, “Measurement ofThree-dimensional Velocity Vectors In a Flow Field Based onSpatio-Temporal Image Correlation,” 3rd International Symposium FLUCOME,pp. 609-615, (1991), C. Brucker, “3-D PIV Via Spatial Correlation in aColor-Coded Light-Sheet,” Experiments in Fluids, 21, pp. 312-314,Springer Publishing House, 1996, and A. Cenedese and A. Paglialunga, “ANew Technique For the Determination of the Third Velocity Component withPIV,” Experiments in Fluids, 8, pp. 228-230, Springer Publishing House,1998.

In M. Raffel et al., “Analytical and Experimental Investigations OfDual-Plane Particle Image Velocimetry,” Optical Engineering 35, 7, pp.2067-2074, (1996), the further suggestion is made to spatially transposea single light section into two light-section positions using a chopperdisk.

Finally, from F. Dinkelacker et al., “Determination of the ThirdVelocity Component with PTA Using an Intensity Graded Light Sheet,”Experiments in Fluids 13, pp. 357-359, Springer Publishing House, 1992,it is already known to modulate the intensity of individual thickerlight sections along a light section depth.

Summarizing, the cited surface methods make it possible to determine thevelocity components of the suspended particles within a plane andtherefore also to analyze the flows in the fluid or gas to be examined.However, they are only capable of analyzing three-dimensional flows inone plane and not in a volume.

Among the spatial measuring methods, i.e., those measuring methods whichpermit the analysis of flows in a volume, stereoscopic methods should bementioned, which are known, by way of example, from R. Racca and J.Dewey, “A Method for Automatic Particle Tracking in a Three-DimensionalFlow Field,” Experiments in Fluids 6, pp. 25-32, Springer PublishingHouse, 1988, or which function using stereoscopic lenses, as proposed byT. Chang et al., “Application of Image Processing to the Analysis OfThree-Dimensional Flow Fields,” Optical Engineering, 23, 3, pp. 282-287,(1984). In this method, the flow field is recorded from differentdirections using two to four cameras.

All of the above-mentioned spatial measuring methods have in common thatthey have a continual illumination of the flow field to be analyzedand/or that the volume to be analyzed is recorded from differentdirections using a plurality of image detectors. Therefore, thesemethods are only partially applicable for practice where setup times,optical accessibility, and limitations regarding direction ofobservation play an important role. The latter, furthermore, alsoapplies to holographic methods.

Finally, from C. Brücker, “Digital-Particle-Image-Velocimetry (DPIV) ina Scanning Light Sheet: 3-D Starting Flow Around a Short Cylinder,”Experiments in Fluids 19, pp. 255-263, Springer Publishing House,(1995), a spatial measuring method is known, in which the volume to beanalyzed is scanned using a drum scanner having a monochromatic laserbeam. In this context, the scattered light characterizing the flow andscattered in the suspended particles is recorded as a function of timeusing a high-speed camera. For this purpose, each individual light-sheetposition in the volume to be analyzed is separately recorded, so thatthe recording of the flow field is tied to the image repetitionfrequency of the camera used. In addition, the separate recording ofeach individual light-sheet position in the detection space generates avery large quantity of data having correspondingly large memoryrequirements.

The objective of the present invention is to carry out the measurementof flow velocities and the analysis of flows in gases and liquids withina detection space in a three-dimensional manner and at the same timemore simply, more rapidly, and more cost-effectively.

SUMMARY OF THE INVENTION

In contrast to the related art, the method and the device according tothe present invention have the advantage of relatively small equipmentexpense, especially with regard to the detection device. Furthermore, itis advantageous that only one observation direction, i.e., only one CCDcolor camera, is required.

In addition, the method according to the present invention has theadvantage that the data sets that arise are relatively small, and thatthey therefore can be processed and evaluated easily andstraightforwardly.

Finally, the attainable resolution, i.e., measuring precision, in themethod according to the present invention is now no longer tied, forexample, to the image repetition frequency of a high-speed camera, butis only limited by the distance and the temporal difference in thegeneration of two adjacent, parallel light sheets which are arranged inspatial succession.

Therefore, it is particularly advantageous if a multiplicity of lightsheets having light of different colors or different frequency spectrumsare used, these colors potentially lying both in the visible frequencyrange as well as in the near ultraviolet or near infrared range. In thiscase, for recording within the detection space the light that isscattered by or emanating from the particle characterizing the flow, aconventional and therefore relatively economical CCD color camera issuitable.

Suitable as the electromagnetic waves, or light, is, on the one hand, apolychromatic light beam, polychromatic here being understood to be alight beam which covers a wider frequency spectrum in the visiblefrequency range and appears, for example, to the human eye as white oras a secondary color, and, on the other hand, if appropriate, aplurality of light beams of this type, which make available in each caseone or a plurality of different colors, i.e., primary colors.

In this context, the light source for this or these light beams can beone or a plurality of lasers or an arrangement of laser diodes, which,if necessary, each generate different colors, secondary or primarycolors (red/yellow/blue). In addition, projection lamps havingpoint-plotting light surfaces are also used.

Particularly advantageous are one or a plurality of polychromatic laserbeams, because in this manner a particularly good collimation andspatial resolution, i.e., separation, of the individual light sheets inthe detection space is achieved.

To assure that, in the raster scanning of the detection space throughthe parallel light sheets at the location of the image detectors, i.e.,of the detection device, the depth of focus produced is good and alwaysat least substantially consistent, it is advantageous if the detectiondevice or the CCD color camera used is provided with an additionaldevice for the continuous or step-by-step adjustment of the depth offocus. In this context, the adjustment of the depth of focus, forexample, using a control unit, is correlated with the raster scanning ofthe detection space via the light sheets that are generated in temporalsuccession.

Well suited to evaluate the images of the detection space recorded bythe CCD color camera, i.e., the detection device, are generally knownalgorithms and evaluation methods from “Particle Image Velocimetry,”which additionally take into account the color information. However,“Particle Tracking Methods” can also be used.

Overall, in the aforementioned methods known to the worker skilled inthe art, it is only necessary to expand them with respect to colorrecognition or frequency or frequency band recognition and with respectto the evaluation of the frequency or color information, for quantifyingthe normal velocity components.

A simple and rapid filtering of the polychromatic light made availableby the light source is advantageously carried out using a generallyknown acoustooptic modulator, which makes possible a color mixing, i.e.,the generation of any and all colors, at a color change frequency thatextends into the MHZ range.

In addition, it is advantageous to provide in the illuminating device acollimator and a polygon scanner having an attached galvanometerscanner, which make it possible to raster scan the detection space at ahigh spatial resolution, i.e., at minimal width and clearer spatialseparation of the individual adjoining light sheets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic sketch of a flow analysis device according topresent invention in a top view.

FIG. 2 depicts a three-dimensional representation of a segment of thedetection space having in addition two segments of two separate lightsheets at two different points in time.

FIG. 3 depicts two images recorded one after the other at the end faceof the detection space for calculating the flow velocity components ofthe individual particles.

FIG. 4 depicts an individual image of the detection space in twoexposures made at different times.

FIG. 5, in a continuation of the detection space depicted in FIG. 4, amultiplicity of sequential scanning processes.

DETAILED DESCRIPTION

The crux of the method according to present invention is that, using anilluminating device, for example, a light source, for emittingelectromagnetic waves in the form of polychromatic light, and downstreamoptical components, it is possible to generate at least approximatelyparallel light sheets, that are multi-colored or that vary in theirfrequency or in their frequency spectrum, which, arranged one after theother spatially and temporally, scan, i.e., raster scan, a detectionspace 25 or an area of detection space 25, and that during this scanningprocess one or a plurality of image detectors, i.e., detection devices,for example, a CCD color camera 16, which is arranged on end face 26 ofdetection space 25, record an image of detection space 25.

For this purpose, as light source 10, in the example discussed, amulticolored light source is used, for example a multicolored laserbeam, which functions either in pulsed-mode or continuous-waveoperation.

Alternatively, however, the multicolored light beam can also be realizedusing differently colored laser diodes or a plurality of lasers ofdifferent frequencies, which then are superimposed using opticalcomponents.

A further possibility for generating a multicolored light beam, inparticular a multicolored laser beam 11, arises when fiber lasers areused.

To achieve a staggering of parallel light sheets, arranged one after theother spatially and temporally in the area of detection space 25,further components are provided downstream of light source 10. Thus thecolor change from one light sheet to the next one takes place, forexample, using an acoustooptic modulator 12 or, alternatively, using anintegrated-optical color mixer.

Generating the different, adjacent, parallel light sheets then takesplace using a collimator 13, which is provided downstream ofacoustooptic modulator 12, using a downstream, generally knowngalvanometer scanner 14, and using a downstream, generally known polygonscanner 15.

These components provided downstream of acoustooptic modulator 12 effecta raster scanning of detection space 25 via monochromatic laser beam11′, emerging from acoustooptic modulator 12, in the form of at leastroughly parallel light sheets 17, 18, 19, 20, 21, 22, that are generatedin spatial succession and in temporal succession. In this context, theterm “monochromatic” is understood only that laser beam 11′, incomparison with laser beam 11, has a reduced frequency spectrum and inparticular a different color than incident laser beam 11. Thus laserbeam 11 can be, for example, white, whereas laser beam 11′ is, forexample, red, blue, or green. Of course, laser beam 11 can also begreen, whereas laser beam 11′ then is, for example, blue or yellow.

Light sheets 17, 18, 19, 20, 21, 22 are therefore distinguished in eachcase by their color as a consequence of the color change effected byacoustooptic modulator 12 on, for example, multicolored or white laserbeam 11, that is supplied to the modulator.

In this context, the raster scanning of detection space 25 is preferablycarried out such that CCD color camera 16 registers an at leastapproximately continuous illumination of detection space 25, i.e., oflight sheets 17, 18, 19, 20, 21, 22.

Recording the image of the flow space can take place, as an alternativeto the image detector, i.e., CCD color camera 16, using a 3-chip specialcamera furnished with interference filters, for example, a so-calledLLT3 camera. In the event this special camera is used, three individualblack-and-white sensors are used, which represent the colors red, green,and blue of an RGB image. In this case, the individual colors are thenreconstructed in a computer by superimposing the individual images andare depicted in false colors.

This procedure is especially suitable if the only light sourcesavailable are those which cover only a small wavelength spectrum, so astherefore to be able nevertheless to realize a larger color spectrum.

Since the distance between the light sheets of the detection device, inparticular CCD color camera 16, is continually changing in response tothe raster scanning of the detection space using parallel light sheets17, 18, 19, 20, 21, 22, to assure an at least approximately constantdepth of focus, in one preferred embodiment of the present invention,provision is made to assign to the detection device a device for thecontinuous or stepwise adjustment of the depth of focus and to correlateit, for example via a generally known control unit, with the temporallychanging position of light sheets 17, 18, 19, 20, 21, 22 in detectionspace 25.

The evaluation of the two-dimensional, color images of detection space25, recorded by the detection device in a frequency- orfrequency-band-selective manner, is then carried out either on the basisof one individual recorded image, in which two or more scanningprocesses are recorded, or on the basis of a plurality of recordedimages, preferably recorded in rapid succession, in which in each caseone or more scanning processes are recorded.

For evaluating the shift of the particles suspended in detection space25, or in the liquid or gas contained therein, and thus for determiningvelocity components v_(x), v_(y), v_(z), which represent directly animage of the local flow conditions predominating in detection space 25,the known methods of “Particle Image Velocimetry”, expanded through theevaluation of color information, or the known “Particle TrackingMethods” are used in the example discussed.

In this manner, the positions of suspended particles 30, 31, 32, 33, 34,35, within individual light sheets 17, 18, 19, 20, 21, 22, can bedetected in a way that is entirely analogous to conventionallight-section methods.

The positions of these particles 30, 31, 32, 33, 34, 35 in the normaldirection (y direction) with respect to light sheets 17, 18, 19, 20, 21,22, are then clearly generated from the determination of the color ofthe specific scattered light, because each color clearly assigns a lightsheet 17, 18, 19, 20, 21, 22, and therefore a corresponding position inthe y direction to particle 30, 31, 32, 33, 34, 35 which is emitting orscattering the light. In this context, the measuring precision in thenormal direction is initially stipulated by the width of specific lightsheet 17, 18, 19, 20, 21, 22, but it can be increased by an optionalanalysis of the intensity distribution of the scattered light signals oftwo adjoining light segment sheets 17, 18, 19, 20, 21, 22, as a functionof the y direction (normal direction).

In order to attain a higher temporal resolution capacity, oneadvantageous embodiment of the present invention also provides that twolight sheets, arranged very rapidly one after the other, scan identicaldetection space 25. A procedure of this type can be realized, forexample, by providing a corresponding second illuminating device, or bymaking available, in addition to a, for example, monochromatic incidentlaser beam 11′, a second, differently colored, incident laser beam,downstream of which the appropriate optical, i.e., acoustoopticcomponents, are arranged, so that the second laser beam, in comparisonto first laser beam 11′, is generated in a spatial offset, and bothlaser beams bring about an offset of light sheets spatially andtemporally, such that two light sheets generated in alternating fashionscan the same detection space 25 one immediately after the other.

The exemplary embodiment of the present invention discussed above isexplained below in greater detail on the basis of FIG. 1. FIG. 1 depictsa flow analysis device 5 having a light source 10 in the form of amulticolored laser, which generates a multicolored laser beam 11. Thismulticolored laser beam 11 is directed at acoustooptic modulator 12,which in a generally known manner filters out defined frequencies orfrequency ranges from the supplied multicolored light and thereforeemits a monochromatic laser beam 11′. For this purpose, acoustoopticmodulator 12 specifically brings about either a color mixing or afiltering of the supplied light. Monochromatic laser beam 11′, emittedfrom acoustooptic modulator 12, therefore changes its color in veryrapid succession. Known acoustooptic modulators make it possible toundertake this color change, for example, in a frequency range of 100kHz up to 1 MHZ.

A multicolored laser beam 11 of this type is, for example, a laser beamwhose color is composed of a plurality of primary colors.

The colors red, green, and blue are preferably used, which aregenerated, for example, by an argon-krypton laser, which emitsmulticolored laser beam 11. Acoustooptic modulator 12 then undertakes amodulation of the intensities of the individual supplied colors inmulticolored laser beam 11 such that a high-frequency color changearises and, in each case, a monochromatic laser beam 11′ is emitted.

Downstream of acoustooptic modulator 12, collimator 13 is then provided,which is configured, for example, as a lens system and which can adjustthe thickness of individual light sheets 17, 18, 19, 20, 21, 22. Thethickness of the individual light sheets preferably lies in the range of100 μm to 1 mm, in particular 500 μm to 1 mm.

The number of light sheets 17,18, 19, 20, 21, 22, arranged one after theother, is at least three, but usually a multiplicity of, for example,100 to 200 light sheets is provided. Detection space 25, has, forexample, dimensions of 10 cm×10 cm×10 cm.

Polygon scanner 15, provided downstream of collimator 13, assures thegeneration of individual light sheets 17, 18, 19, 20, 21, 22 frommonochromatic laser beams 11′, which are supplied in temporalsuccession. Alternatively, in place of polygon scanner 15, it is alsopossible to use one or a plurality of generally known cylinder lenses.Polygon scanner 15 for this purpose preferably rotates at 20,000 to60,000, in particular 40,000, revolutions/min. The scanning rate isadvantageously adjusted to the measuring task and it can, in principle,be increased into the MHZ range, if necessary using optical components.

Overall, monochromatic laser beam 11′, high-frequency modulated in itscolor, is conveyed in one sheet so rapidly that CCD color camera 16,provided as image detector, records a continuous illumination ofindividual sheets.

Galvanometer scanner 14, provided downstream of polygon scanner 15,functions to shift the differently colored, parallel light sheets, sothat they, being at least approximately parallel, and arranged inspatial succession, scan detection space 25, the colors of theseparallel light sheets 17, 18, 19, 20, 21, 22, arranged one behind theother, at the same time, being different.

In this connection, it is important that the shift of light sheets 17,18, 19, 20, 21, 22, takes place synchronously with the color change ofacoustooptic modulator 12, so that a volume arises of differentlycolored light sheets 17, 18, 19, 20, 21, 22, lying at leastapproximately parallel to each other. For this purpose, appropriate,undepicted, generally known control components are provided.

The CCD color camera is installed for recording the image of detectionspace 25 at end face 26 of detection space 25.

FIG. 2 illustrates once again the illumination of a segment of detectionspace 25 using different light sheets. Specifically, in FIG. 2, fouradjoining light sheets 17, 18, 19, 20 are depicted, which are spatiallyoffset with respect to each other and are illuminated in temporalsuccession using light of different colors. Moreover, by way of example,one single scattered particle 30 is provided, which moves between twotime points t₁ and t₂ from a first position in light sheet 18 to asecond position in light sheet 17. For emphasis, this is depicted onceagain separately in FIG. 2.

The x and z coordinates of the position of scattered particle 30 indetection space 25 are directly generated from the image of CCD colorcamera 16. From the different color of scattered particle 30, resultingfrom its position in two different light sheets 18 and 17, at times t₁and t₂, on the one hand, it is then initially possible to determine theposition of particle 30 in the y direction at times t₁ and t₂ and, onthe other hand, from the information concerning time difference ΔTbetween t₁ and t₂, in addition to the flow velocities of scatteredparticle 30 in the x and z directions, the flow velocity component inthe y direction is also determined.

FIG. 3 illustrates this schematically in the example of two imagesrecorded one after the other at time points t₁ and t₂ at end face 26 ofdetection space 25 by CCD color camera 16. In this context, scatteredparticles 31, 32, 33, suspended in detection space 25, generate ascattering of the impinging light, the different symbols for scatteredparticles 31, 32, 33, in FIG. 3, standing for the different colors ofthese scattered particles 31, 32, 33.

Specifically, both images at time points t₁ and t₂ in FIG. 3 stand fortwo entire scanning processes of detection space 25, in other words, allof the parallel, differently colored light sheets were generatedprecisely twice, and two images of detection space 25 were recorded. Ineach image, a complete scanning process is therefore recorded.

From the knowledge of time difference Δt=t₂−t₁ and from the changes inthe positions of scattered particles 31, 32, 33 in the x direction andin the z direction, their velocity components can immediately becalculated in the x and z directions. The velocity components in the ydirection of individual scattered particles v_(y)=Δy/Δt is then yieldedby evaluating the colors, i.e., the changes in color, of scatteredparticles 31, 32, 33 between times t₁ and t₂.

The precision of the determination of velocity component v_(y), in thiscontext, is a function of the thickness of the individual light sheets.

FIG. 4 depicts a typical recorded image in which two complete scanningprocesses have been recorded in one image of CCD color camera 16. Thesetwo records were taken in rapid succession at time points t₁ and t₂.Typical rates of repetition of the scanning processes of detection space25, in this context, lie within the range from 100 Hz to 1 kHz,corresponding to the flow velocities usually observed in fluids in theorder of magnitude of m/sec. However, using the method discussed,scanning rates in the MHZ range are also possible in principle in thiscase as well.

The size of scattered particles 30, 31, 32, 33, 34, 35 typically lie inan order of magnitude of 1 μm to 20 μm.

In FIG. 4, different symbols for scattered particles 31, 32, 33, as inFIG. 3, stand for different colors of these particles. In this context,the same symbols mean specifically that the individual scatteredparticle is located in the same light sheet at times t₁ and t₂.

Furthermore, it should be noted that FIGS. 3 through 5 only serveillustrative purposes and are radically simplified diagrammaticsketches.

FIG. 5, as an extension of FIG. 4, depicts a recorded image in which atotal of seven complete scanning processes have been recorded at timepoints t₁, through t₇. Thus in FIG. 5, each of two depicted scatteredparticles 34 and 35 was recorded by a total of 7 scanning processes, sothat for each scattered particle 34, 35, a series of sequential imagepoints results. Within this series of image points, once again the colorof the particle characterizes its position in detection space in the ydirection.

Furthermore, it should be noted that the records according to FIG. 3 canbe evaluated using cross correlation methods modified in the usualmanner, as they are used in “Particle Image Velocimetry.”

The records in accordance with FIGS. 4 and 5 can also be evaluated usingmodified correlation algorithms, especially the autocorrelation, i.e.,the “Particle Tracking Method.”

Finally, it should be emphasized that the evaluation in the case of FIG.5 can take place even without evaluation algorithms, simply through aqualitative spatial assessment of the flow field, by taking account ofthe paths of the individual scattered particles and the color changealong these paths.

What is claimed is:
 1. A method for performing an analysis of a flow ina detection space, comprising the steps of: detecting electromagneticwaves that one of: i) at least partially emanate from, and ii) arescattered by particles that are contained in the detection space andthat characterize the flow; generating at least two roughly parallellight sheets in accordance with the electromagnetic waves, theelectromagnetic waves including one of: i) different frequencies, andii) different frequency spectrums, the at least two light sheets ofeither different frequencies or different frequency spectrums beinggenerated in temporal succession relative to one another; arranging theat least two light sheets in spatial succession; and scanning thedetection space at least in areas using the at least two light sheets.2. The method according to claim 1, wherein: the method is for one of athree-dimensional determination of a flow velocity component and athree-dimensional visualization of the flow in one of a fluid and a gas.3. The method according to claim 1, wherein: the electromagnetic wavesare in the form of light of different colors in a visible frequencyrange.
 4. The method according to claim 1, further comprising the stepof: recording the scanning of the detection space in accordance with anoperation of at least one image detector.
 5. The method according toclaim 4, wherein: the at least one image detector includes at least oneCCD color camera.
 6. The method according to claim 1, wherein: the atleast two light sheets are generated by a multicolored light beam usinglight of different colors.
 7. The method according to claim 1, wherein:the at least two light sheets are generated in temporal succession inaccordance with light from at least two light sources, the light beingone of different frequencies and of different frequency spectrums. 8.The method according to claim 6, wherein: the multicolored light beam isused in one of a pulsed-mode operation and a continuous-wave operation.9. The method according to claim 7, wherein: the at least two lightsources function in one of a pulsed-mode operation and a continuous-waveoperation.
 10. The method according to claim 4, wherein: the at leasttwo light sheets scan the detection space such that the at least oneimage detector records an illumination of the detection space, theillumination being at least approximately continuous in time.
 11. Themethod according to claim 4, wherein: the at least one image detector,during the scanning of the detection space, is one continuouslyreadjusted and stepwise readjusted in a depth of focus thereof, suchthat the at least two light sheets form an image at a location of the atleast one image detector that is, in each case, at least fairly sharp.12. The method according to claim 1, wherein: the scanning of thedetection space includes at least two scannings of the detection spaceperformed in rapid temporal succession.
 13. The method according toclaim 4, further comprising the step of causing the at least one imagedetector to record a two-dimensional color image of the detection space,wherein: in the two-dimensional color image a light that is one ofemanating from and scattered by the particles is recorded by at leasttwo sequential scannings of the detection space.
 14. The methodaccording to claim 4, further comprising the step of: causing the atleast one image detector to record a two-dimensional color image of thedetection space, wherein: a light that is one of emanating from andscattered by the particles is recorded in each case by at least onescanning of the detection space, in at least two images that arerecorded in rapid succession.
 15. The method according to claim 1,further comprising the step of: evaluating an image of the detectionspace in accordance with one of a particle tracking algorithm and acorrelation operation, including one of color information, a frequency,and frequency band information.
 16. The method according to claim 1,wherein the detection space is a three-dimensional detection space, themethod further comprising the step of: determining at least one of alocation of the particles, within a scanned area of thethree-dimensional detection space, and a spatial shift of the particlesfrom detected light as a function of time in accordance with anevaluation of a recorded, two-dimensional, color image of the detectionspace.
 17. The method according to claim 16, further comprising the stepof: determining local flow velocities of the particles by taking intoaccount a time duration between scanning processes.
 18. A device forperforming an analysis of a flow in a detection space, comprising: anarrangement for detecting electromagnetic waves that one of: i) at leastpartially emanate from, and ii) are scattered by particles that arecontained in the detection space and that characterize the flow; atleast one illuminating device for generating at least approximatelyparallel light sheets in accordance with the electromagnetic waves, thelight sheets illuminating at least partially the detection space, andthe electromagnetic waves including one of: i) different frequencies,and ii) different frequency spectrums, the at least one illuminatingdevice generating the light sheets of either different frequencies ordifferent frequency spectrums in temporal succession relative to oneanother; an arrangement for arranging the light sheets in spatialsuccession; and at least one detection device for recordingtwo-dimensional images of at least one area of the detection space inone of: i) a frequency-selective manner, and ii) afrequency-band-selective manner.
 19. The device according to claim 18,wherein: the at least one illuminating device includes at least onelight source for generating the electromagnetic waves in the form oflight and to have one of the different frequencies and the differentfrequency spectrums.
 20. The device according to claim 19, wherein: theat least one light source includes a laser.
 21. The device according toclaim 18, further comprising: a multicolored light source for generatinglight that can be split up into a plurality of colors in accordance witha frequency-sensitive component.
 22. The device according to claim 21,wherein: the multicolored light source includes a multicolored laser.23. The device according to claim 21, wherein: the frequency-sensitivecomponent includes one of an acoustooptic modulator, a grating, and aprism.
 24. The device according to claim 18, wherein: the at least oneilluminating device includes a collimator, a polygon scanner, and agalvanometer scanner.
 25. The device according to claim 18, wherein: theat least one detection device is positioned on at least one end face ofthe detection space.
 26. The device according to claim 25, wherein: theat least one end face includes an end face that is parallel to the lightsheets.
 27. The device according to claim 18, wherein: the at least onedetection device includes at least one color camera for recording thetwo-dimensional images of the detection space in color.
 28. The deviceaccording to claim 27, wherein: the at least one detection deviceincludes a CCD color camera.
 29. The device according to claim 27,wherein: the at least one color camera includes an arrangement foradjusting a depth of focus.
 30. The device according to claim 18,further comprising: an evaluation unit for at least one of evaluatingand storing the two-dimensional images.
 31. A new method for performingan analysis of a flow in a detection space, comprising: detectingelectromagnetic waves that one of: i) at least partially emanate from,and ii) are scattered by particles that are contained in the detectionspace and that characterize the flow; generating at least two roughlyparallel light sheets in accordance with the electromagnetic waves, theelectromagnetic waves including one of: i) different frequencies, or ii)different frequency spectrums, the at least two light sheets of eitherdifferent sequences or different frequency spectrums being generated intemporal succession relative to one another and in spatial successionrelative to one another; and scanning the detection space at least inareas using the at least two light sheets.
 32. A device for performingan analysis of a flow in a detection space, comprising: an arrangementconfigured to detect electromagnetic waves that one of: i) at leastpartially emanate from, and ii) are scattered by particles that arecontained in the detection space and that characterize the flow; atleast one illuminating device configured to generate at leastapproximately parallel light sheets in accordance with theelectromagnetic waves, the light sheets illuminating at least partiallythe detection space, and the electromagnetic waves including one of: i)different frequencies, or ii) different frequency spectrums, the atleast one illuminating device configured to generate the light sheets ofother different frequencies or different frequency spectrums in temporalsuccession relative to one another and in spatial succession relative toone another; and at least one detection device configured to recordtwo-dimensional images of at least one area of the detection space inone of: i) a frequency-selective manner, or ii) afrequency-band-selective manner.